1,4-diaryl-2-fluoro-2-butenes and a method for their preparation are described in U.S. Pat. No. 5,998,673. Said compounds are useful as insecticidal and acaricidal agents and for protecting plants from damage caused by insect and acarid attack and infestation. Although U.S. Pat. No. 5,998,673 discloses and claims optical isomers of said 1,4-diaryl-2-fluoro-2-butenes, it does not provide a method for their preparation.
It is therefore an object of the present invention to provide a process for the preparation of chiral 1,4-diaryl-2-fluoro-2-butenes.
It is also an object of the present invention to provide intermediates useful in said process.
These and other objects of the present invention will become more apparent from the detailed description thereof set forth below.
There is provided a process for the preparation of a chiral compound of formula I 
wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy, C1-C4haloalkoxy or hydroxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one
to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is C1-C4alkyl, C1-C4haloalkyl, C3-C6cycloalkyl or C3-C6halocycloalkyl;
Ar1 is phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
biphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenoxypyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylpyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzoylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, and
the (E)- and (Z)-isomers thereof, which process comprises the following steps:
a) treating a racemic ester of formula II 
wherein Ar and R are defined as hereinabove and R4 is C1-C4alkyl with an esterase to form a first mixture of either R-acid IIIa and S-ester IIIb 
or of S-acid IIIc and R-ester IIId 
b) separating said acid IIIa or IIIc from said ester IIIb or IIId;
c) reducing said acid IIIa or IIIc or said ester IIIb or IIId to obtain a chiral alcohol IV having the R- or S-configuration 
b) reacting said chiral alcohol with an arylsulfonyl halide Ar2SO2X
wherein Ar2 is phenyl, p-chlorophenyl, or p-tolyl, and X is chloro, bromo or fluoro to afford a sulfonate of formula V 
e) reacting said sulfonate V with a cyanide-delivering agent to afford a nitrile of formula VI 
f) hydrolysing said nitrile VI to afford an acid of formula VII 
g) esterifying said acid VII with an alcohol R1OH, wherein R1 is C1-C4 alkyl to afford an ester of formula VIII 
h) fluorinating said ester to afford a fluoro-ester of formula IX 
i) reacting said fluoro ester with an aldehyde Ar1CH2CHO, wherein Ar1 is defined as hereinabove, in a solvent in the presence of a base to afford a second mixture of 4 chiral diastereomeric hydroxy-esters of formula X 
j) optionally separating said second mixture X into a third mixture Xa and a fourth mixture Xb, each mixture having two chiral diastereomers;
k) treating said hydroxy-ester mixture X, Xa or Xb with an acylating agent R2COX1, wherein R2 is C1-C4alkyl and X1 is Cl, Br or R2COO, to afford a fifth mixture of 4 chiral diastereomeric acyloxy esters XI, a sixth mixture of 2 acyloxy esters of formula XIa, or a seventh mixture of 2 chiral diastereomeric acyloxy esters XIb 
l) optionally separating said sixth or seventh mixture into essentially pure chiral diastereomeric acyloxy esters;
m) hydrolyzing said pure chiral acyloxy esters or mixtures of esters of formula XI to afford a hydroxy-acid of formula XII 
and
n) heating said hydroxy-acid XII with an arylsulfonyl halide Ar3SO2X2, wherein Ar3 is phenyl, p-chlorophenyl, or p-tolyl, and
X2 is chloro or bromo to afford the desired chiral compound of formula I.
The invention further provides chiral intermediate compounds useful in the process of this invention.
Although chiral 1,4-diaryl-2-fluoro-2-butenes are described in U.S. Pat. No. 5,998,673, no method for their preparation is disclosed.
Advantageously, the present invention provides a method for the preparation of chiral compounds of formula I 
wherein Ar, R and Ar1 are defined as above.
In accordance with the process of this invention racemic ester II is enzymatically hydrolyzed with an esterase to afford a first mixture of acid IIIa having the R-configuration, and unhydrolyzed ester IIIb, having the S-configuration, which is separated. Said acid IIIa or said ester IIIb is reduced to obtain a chiral alcohol IV having the R- or S-configuration; said alcohol is reacted with an arylsulfonyl halide Ar2SO2X to afford a sulfonate of formula V; said sulfonate is treated with a cyanide-delivering agent to afford a nitrile of formula VI; said nitrile is hydrolyzed to yield an acid of formula VII; said acid is esterified with an alcohol R1OH to yield an ester of formula VIII; said ester is fluorinated to afford a fluoro-ester of formula IX; said fluoro-ester is reacted with an aldehyde Ar1CH2CHO in a solvent in the presence of a base to afford a second mixture of 4 chiral diasteromeric hydroxy-esters of formula X; optionally said second mixture can be separated into a third mixture Xa and a fourth mixture Xb, each mixture having two chiral diastereomers; said hydroxy-ester mixture X, Xa, or Xb is treated with an acylating agent R2COX, to afford a fifth mixture of 4 chiral diasteromeric acyloxy esters XI, a sixth mixture of 2 acyloxy esters of formula XIa, or seventh mixture of chiral diasteromeric acyloxy esters XIb; optionally, said sixth or seventh mixture can be separated into to essentially pure chiral diastereomeric acyloxy esters; said pure chiral acyloxy esters or mixtures of esters of formula XI are hydrolyzed to a hydroxy acid of formula XII; and finally, said hydroxy acids are heated with an arylsulfonyl halide Ar3SO2X2 to afford the desired chiral compound of formula I. The process is depicted in Flow Diagram I wherein R4 is depicted as methyl.
The wavy lines in structural formula I represent either the E isomeric or the Z isomeric configuration about the carbon-carbon double bond. 
Non-polar solvents suitable for use in the process of the invention are essentially water-free solvents such as aromatic hydrocarbons (e.g. toluene, benzene, xylene, naphthalene or the like, preferably toluene), halogenated aromatic hydrocarbones (e.g. chlorobenzene, dichlorobenzene or the like), hydrocarbons (e.g. chloroform, methylene chloride, dichlorethane, or the like, or any of the conventional, preferably water imiscible, organic non-polar solvents.
Preferred non-polar solvents suitable for use in the process of the invention are hydrocarbons and aromatic hydrocarbons such as hexane, heptane, toluene, ethylbenzene or the like.
Polar aprotic solvents suitable for use in the inventive process are dimethylformamide, dimethyl-sulfoxide, tetrahydrofuran, diethyl ether, or the like.
Preferred polar aprotic solvents suitable for use in the process of the invention are dimethylformamide and dimethylsulfoxide.
Derivitizing agents suitable for use in the formation of V are triarylphosphine/trialkylphosphines such as triphenylphosphine and triethylphosphine and carbon tetrahalides such as carbon tetrachloride and carbon tetrabromide as well as arylsulfonyl halides such as p-toluene sulfonyl chloride, p-toluene sulfonyl bromide, p-toluene sulfonyl fluoride, benzenesulfonyl bromide, benzenesulfonyl chloride, benzenesulfonyl fluoride, p-chlorobenzenesulfonyl bromide, p-chlorobenzenesulfonyl chloride and p-chlorobenzenesulfonylfluoride or alkylsulfonyl halides such as methane sulfonyl chloride, preferably p-toluene sulfonyl chloride. Suitable bases are resin-bound tertiary organic bases such as polystyrene diisopropyl ethylamine and tertiary organic bases such as triethyl amine and diisopropyl ethyl amine and pyridine, preferably triethlamine. Reaction temperatures may vary from about 0xc2x0 C. to reflux, preferably from about 25xc2x0 C. to about 50xc2x0 C., more preferably about 25xc2x0 C.
Cyanide delivering agents suitable for the formation of nitrile VI are metal cyanides, alkali earth metal cyanide and alkali metal cyanide such as potassium cyanide, zinc cyanide and sodium cyanide, preferably sodium cyanide. Reaction temperatures may vary from about 25xc2x0 C. to about 180xc2x0 C., preferably from about 50xc2x0 C. to about 125xc2x0 C., more preferably about 90xc2x0 C.
Suitable agents for the hydrolysis of nitrile VI are aqueous acids such as sulfuric acid or hydrochloric acid in the presence of or without the presence of alcohol such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol and t-butyl alcohol, aqueous alkali or alkali earth bases such as potassium hydroxide, calcium hydroxide and sodium hydroxide, preferably sodium hydroxide. Reaction temperatures may vary from about 25xc2x0 C. to about 100xc2x0 C., preferably from about 50xc2x0 C. to about 100xc2x0 C., more preferably about 100xc2x0 C.
Reaction temperatures suitable for the esterifiecation of acid VII vary from about xe2x88x9210xc2x0 C. to about 40xc2x0 C., preferably about xe2x88x9210xc2x0 C. to about 10xc2x0 C., more preferably about 0xc2x0 C.
Bases suitable for the generation of the anion of if ester VIII are alkali metal hexaalkylsilylamides such as lithium hexamethylsilylamide or sodium hexamethylsilylamide, alkali metal dialkyl amides such as sodium diisopropylamide, metal hydrides such as sodium hydride and potassium hydride, preferably lithium diisopropyl amide.
Reaction temperatures vary from about xe2x88x9278xc2x0 C. to about 25xc2x0 C., preferred starting temperature is about xe2x88x9278xc2x0 C., with the ending temperature about 25xc2x0 C.
Suitable bases for treating fluoroester IX are metal hydrides such as sodium hydride and potassium hydride, alkali metal hexa-alkylsilylamide such as sodium hexamethylsilylamide or lithium hexamethysilylamide, alkali metal dialkylamides such as sodium diisopropylamide or lithium diisopropylamide, preferably lithium diisopropylamide.
Suitable bases for the formation of I are pyridine and substituted pyridines, preferably collidine. Reaction temperatures vary from about 25xc2x0 C. to about 200xc2x0 C., preferably from about 100xc2x0 C. to about 200xc2x0 C., more preferably from about 170xc2x0 C. to about 180xc2x0 C.
In actual practice, racemic ester II in water is treated with an esterase enzyme, preferably horse liver esterase, preferably between pH 7.1-8.0 to yield a first mixture of either R-acid IIIa and S-ester IIIb or S-acid IIIc and R-ester IIId; said acid can be separated from said ester by standard extraction techniques, preferably with aqueous sodium bicarbonate followed by acidification with mineral acid, preferably dilute hydrochloric acid and reextraction, or more preferably by chromatographic techniques, preferably on silica gel; said acid IIIa or IIIc is reduced with diborane, or said ester IIIb or IIId is reduced with diisobutylaluminum hydride to afford chiral alcohol IV having the R- or the S-configuration; said alcohol IV is reacted with at least one molar equivalent of a sulfonyl halide Ar2SO2Cl, preferably an arylsulfonyl chloride in a non-polar aprotic solvent, preferably methylene chloride, in the presence of at least one molar equivalent of a base, preferably a tertiary organic base, more preferably triethylamine to afford sulfonate V; said sulfonate V is reacted with a cyanide-delivering agent, preferably an alkali metal cyanide, more preferably sodium cyanide, in a polar aprotic solvent, preferably dimethylsulfoxide, to yield nitrile VI; nitrile VI is hydrolized in the presence of aqueous acid or base, preferably dilute aqueous sodium hydroxide followed by acidification of the resulting salt with strong mineral acid, preferably concentrated hydrochloric acid, to yield acid VII. Acid VII is esterified with an alcohol R1OH, preferably present in excess, in the presence of a strong acid catalyst, preferably anhydrous hydrogen chloride gas, to yield ester VIII.
Said ester is fluorinated, preferably by generating its anion with a base, preferably an alkali metal amide, more preferably lithium diisopropyl amide in an aprotic solvent, preferably tetrahydrofuran, followed by quenching said anion with an electrophilic fluorinating agent, preferably an N-fluoroimide, more preferably N-fluorobenzenesulfonimide to yield fluoro ester IX; said fluoro ester IX is reacted with an aldehyde Ar1CH2CHO in the presence of a base, preferably an alkali metal amide, more preferably lithium diisopropylamide, in an aprotic solvent, preferably tetrahydrofuran, to afford a second mixture of 4 chiral diasteromeric hydroxy-esters of formula X; advantageously said second mixture X may be optionally separated, preferably by chromatographic techniques, more preferably on silica gel, into a third mixture Xa and a fourth mixture Xb, each mixture having two chiral diastereomers; said hydroxy-ester mixture X, Xa or Xb is treated with an acylating agent R2COX1, preferably an acid anhydride (R2CO)2O, more preferably acetic anhydride, in a non-polar solvent, preferably methylene chloride in the presence of an acylation catalyst, preferably N,N-dimethylaminopyridine, to afford a fifth mixture of 4 chiral diastereomeric acyloxy esters XI, a sixth mixture of 2 aryloxy esters of formula XIa, or a seventh mixture of 2 chiral diasteromeric acyloxy esters of formula XIb; advantageously said sixth or seventh mixture are optionally separated preferably by chromatographic techniques, more preferably with silica gel into essentially pure chiral diastereomeric acyloxy esters; said pure chiral acyloxy esters or mixtures of esters of formula XI are hydrolyzed with acid or base, preferably dilute aqueous metal hydroxide, more preferably dilute aqueous sodium hydroxide followed by acidification with a strong mineral acid, preferably concentrated hydrochloric acid, to afford a hydroxy-acid of formula XII; said hydroxy-acid is treated in the presence of an aryl-sulfonyl halide Ar3SO2X2, preferably an arylsulfonyl chloride, more preferably p-toluene sulfonyl chloride, to afford the desired chiral compound of formula 1.
The present invention also provides chiral compounds of formula XIII 
wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy, C1-C4haloalkoxy or hydroxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is C1-C4alkyl, C1-C4haloalkyl, C3-C6cycloalkyl or C3-C6halocycloalkyl;
Ar1 is phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
biphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenoxypyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylpyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzoylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, and
R3 is H or C1-C4alkyl; and
Z is H or COR2, wherein R2 is C1-C4alkyl.
Preferred compounds of the present invention are those wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups; and
R is C1-C4alkyl or C3-C6cycloalkyl.
More preferred compounds are those wherein
Ar1 is phenyl optionally substituted with one to three halogen groups; and
R is C3-C6cycloalkyl.
Most preferred compounds are those selected from the group consisting of
methyl (2S,3S)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3R)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3R)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3S)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3S)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3R)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3R)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3S)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3S)-3-(acetyloxy)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3R)-3-(acetyloxy)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3R)-3-(acetyloxy)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3R)-3-(acetyloxy)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3S)-3-(acetyloxy)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3R)-3-(acetyloxy)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2R,3S)-3-(acetyloxy)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
methyl (2S,3R)-3-(acetyloxy)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)butanoate;
(2S,3S)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2R,3R)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2R,3S)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2S,3R)-2-[(S)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2S,3S)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2R,3R)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid;
(2R,3S)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid, and
(2S,3R)-2-[(R)-(4-chlorophenyl)(cyclopropyl)methyl]-2-fluoro-4-(4-fluoro-3-phenoxyphenyl)-3-hydroxybutanoic acid.
The present invention additionally provides chiral compounds of formula XIV 
wherein
Q is xe2x80x94CO2H; xe2x80x94CO2CH3; xe2x80x94CH2OH; xe2x80x94CH2OSO2Ar2; xe2x80x94CH2CN; xe2x80x94CH2CO2H; xe2x80x94CH2CO2R1; or xe2x80x94CHFCO2R1;
Ar2 is phenyl, p-chlorophenyl, or p-tolyl; and
R1 is C1-C4alkyl.
Most preferred compounds are selected from the group consisting of
(2R)-2-(4-chlorophenyl)-2-cyclopropylethyl 4-methylbenzenesulfonate;
(2S)-2-(4-chlorophenyl)-2-cyclopropylethyl 4-methylbenzenesulfonate;
(3R)-3-(4-chlorophenyl)-3-cyclopropylpropanenitrile;
(3S)-3-(4-chlorophenyl)-3-cyclopropylpropanenitrile;
(3R)-3-(4-chlorophenyl)-3-cyclopropylpropanoic acid;
(3S)-3-(4-chlorophenyl)-3-cyclopropylpropanoic acid;
methyl (3R)-3-(4-chlorophenyl)-3-cyclopropylpropanoate;
methyl (3S)-3-(4-chlorophenyl)-3-cyclopropylpropanoate;
methyl (3R)-3-(4-chlorophenyl)-3-cyclopropyl-2-fluoropropanoate;
methyl (3S)-3-(4-chlorophenyl)-3-cyclopropyl-2-fluoropropanoate;
In order to present a clear understanding of the invention, the following examples are set forth below. These examples are merely illustrative, and are not to be understood as limiting the scope and underlying principles of the invention in any way.